The goals of this project are to: (1) demonstrate the feasibility of quantitative measurement of natural gas leaks using a multi-spectral scanner and (2) design, fabricate, and field demonstrate a cost effective, hand-held, multi-spectral scanner capable of detecting natural gas leaks in live gas pipelines.

Photograph of the laboratory scale scanner mounted on a tripod

Performer

En-Urga Inc. – project management and research product development

Location:
West Lafayette, Indiana 47906

Background

A wide variety of methods are employed to detect natural gas pipeline leaks, ranging from manual inspection using trained dogs, to advanced, satellite based, hyper-spectral imaging. These methods can be classified as non-optical and optical methods. The primary non-optical methods include acoustic monitoring, gas sampling, soil monitoring, flow monitoring, and software-based dynamic modeling. Optical methods of leak detection can be classified as either passive or active. Passive methods capture electromagnetic radiation reflected or emitted from the area being imaged, while active methods illuminate the area with a laser or broad band source and record the result. Multi-spectral imaging (MSI) is a passive optical remote sensing approach that records data from multiple portions of the spectrum (e.g., ultraviolet, infrared and visible). The combination of multiple images can be used to identify items that might otherwise escape detection. Hyper-spectral imaging (HSI) creates a larger number of images from contiguous regions of the spectrum, typically with much finer resolution.

If a laser is used to illuminate the area above a pipeline, the absorption or scattering caused by natural gas molecules above the surface can be monitored using an array of sensors at specific wavelengths. If there is significant absorption or scattering above a pipeline, then a leak can be presumed to exist. The basic techniques for such active monitoring techniques include: Tunable Diode Laser Absorption Spectroscopy (TDLAS), Laser Induced Fluorescence (LIF), Coherent Anti-Raman Spectroscopy (CARS), Fourier Transform Infrared Spectroscopy (FTIS), and evanescent sensing.

The design of a laboratory scale multi-spectral scanner for detecting natural gas leaks in pipelines is underway. Experimental prototype (“breadboard” testing of the printed circuit board (PCB) design has been completed and the PCB’s have been designed. Mechanical parts for the scanner are being fabricated and development of the data acquisition board programming is ongoing. Once the design and fabrication of the multi-spectral scanner is complete, the scanner will be tested under laboratory conditions using simulated natural gas leaks. Radiation emission intensity will be evaluated at a minimum of three wavelengths. Based on the results of the laboratory testing, a portable, field deployable prototype multi-spectral scanner will be designed and fabricated. This will incorporate, at a minimum, the following components: scanner, optics, three element sensor, printed circuit board, LCD display unit, and battery pack. Following the construction of the prototype, field tests will be conducted to validate the operation and performance of the multi-spectral scanner. These tests will be conducted on live gas pipelines at sites to be identified by En-Urga and will be conducted under conditions that clearly demonstrate the ability of the scanner to detect actual natural gas pipeline leaks.

Impact

Current ground based methods for the detection of natural gas pipeline leaks are extremely limited in distance and in many cases require being immersed in the leak plume itself. The scanner under development is being designed to detect leaks at a distance of approximately 50 feet. This allows for flexible, standoff leak detection and eliminates the need for detection within the gas plume. In addition, the scanner allows for rapid leak detection over a significantly larger surface area, at potentially reduced cost.

Designed and fabricated a laboratory scale multi-spectral scanner which includes the optical design for the scanner (using Zemax optical design software), the electronic design for the scanner (using Protel Electronic Design software), and the complete mechanical engineering design which is modular in nature with the scanner and optics in one module and the detector and PCB in another module. The scanner was designed to operate directly over the pipeline and in all instances, within 50 feet from the leak.

Completed laboratory scale evaluation of the scanner at En-Urga Inc. with a 10 standard cubic feet per hour (SCFH) natural gas leak. Detection was demonstrated with a stationary scanner.